WASHINGTON—U.S. Defence Secretary Leon Panetta is ending the ban on women serving in combat in the military, potentially opening up more than 200,000 positions on the front lines and possibly also jobs with elite commando units.

Pentagon officials said Wednesday that Panetta gave the armed services until 2016 to ask for special waivers if they believe any positions should remain closed to women.

Although women have never been assigned to American front-line fighting units, the decision specifically overturns a 1994 rule that barred women from serving with smaller ground combat units.

Panetta’s decision was seen as a recognition of women’s contributions to the wars in Iraq and Afghanistan. Because of the demand for troops, women often found themselves on the front lines serving as drivers, medics, mechanics and other roles when commanders attached their units to combat battalions. They didn’t receive combat decorations or other special recognition, however.

The move also will help women climb the military ranks. Female service members have struggled to gain promotions in part because of their lack of combat experience; the Pentagon’s first four-star female general, Ann Dunwoody, wasn’t promoted until 2008.

The Pentagon took an initial step last February when it opened 14,000 combat-related jobs, mostly in the army, to female service members. The new policy would open up to women more than 200,000 combat jobs, including in army and marine infantry units.

Canada has allowed women to serve in combat for more than 20 years.

Tammy Duckworth, a congresswoman who lost both of her legs while serving in the Illinois Army National Guard in Iraq, applauded the Pentagon’s move.

“The decision to allow women to serve in combat will allow the best man or woman on the front line to keep America safe,” Duckworth, a Democrat from Illinois, said in a statement Wednesday. “As a combat veteran, I know the inclusion of women in combat roles will make America safer and provide inspiration to women throughout our country.”

Duckworth was the first woman injured in combat ever elected to national office, when she ousted former Republican Rep. Joe Walsh this past November.

“There has always been some level of opposition to increasing the diversity in our military whether it has been minorities or women. It is clear that the inclusion of groups like African Americans and Asians has made our military stronger,” Duckworth added.